The 1820s convict brick cottage, at 62 Main Road, Perth, looked ideal on the exterior, however a bit of research found some serious flaws.

Mrs Cox said although previous owners had "lovingly restored" the property - with good intentions - the fix-up job had proven detrimental.

She said a concrete base, in place of wooden floorboards, and a cement render on its walls meant the cottage's convict bricks were deteriorating.

"When I went to repair the wall, I found the cottage was actually really wet," Mrs Cox said.

"The door posts were rotting and crystals were starting to form on some of the paintwork - what I didn't know was that it was plasterer's rising damp."

She said a phone call to Heritage Tasmania and heritage restorers soon put her on the right track to see the building preserved.

"Convict brick is really soft, it's not fired as we do today," Mrs Cox said.

"The render on the walls had been repaired with cement - cement itself won't take up moisture, so it puts all of that straight into the walls.

"That brings out the salt and perishes the bricks."

Restorers worked to place a chemical water barrier between the walls and floor, and layered appropriate lime render on the walls.

"Most people don't know about these things," Mrs Cox said.

"I called some renderer and they said to put cement render on . . . and to put cement floors in, that is what kills the building.

"People don't seem to want to deal with Heritage Tasmania, because they think it will cost a lot of money and stop them from doing things to the building.

"If, initially, it had been done properly it wouldn't have cost any extra."